Christiana Cargo Trike - Other projects have had priority ...

Most bike builders do their work in the summer.  Mine has actually been moved to the winter when it is too rainy to work on outside projects.  DMV has grounded my wife for awhile, so I am considering making a cargo trike that she can ride to the local store.  Something along the lines of a Christiana trike.

I'm thinking of using a bottom bracket from a single-piece crank as the pivotal foundation for the cargo box.  And attach that to the end of of a large square tube running from the BB that the rider pedals.  Although that round handle is nice, if you had more than one-speed, how would you replace a broken twist-grip shifter?  I'll have to think about that when I get to that point.  I think I'll start with the box frame and the rear frame and see what I have to do to connect them together.  :)